Expansion anchors are known, for example, from EP 1 892 424 A2, which include an anchor bolt and an expansion sleeve. They are used to secure a component to a substrate. For anchoring the expansion anchor in the substrate, the expansion sleeve is inserted, in particular, hammered, into a prepared bore with the aid of the anchor bolt. The anchor bolt is then withdrawn a certain extent from the bore, the expansion sleeve in this case remaining essentially fixed in place due to its interaction with the surrounding bore hole wall. Consequently, an axial displacement of the anchor bolt occurs relative to the expansion sleeve, and the expansion section of the anchor bolt is refracted axially into the expansion sleeve. As a result of the retraction, the expansion sleeve in turn is radially expanded and the anchor is thereby anchored in the bore hole. This principle also forms the basis of the present invention.
The extraction of the anchor bolt in order to expand the expansion sleeve may be accomplished according to EP 1 892 424 A2, for example, by tightening a nut situated on the anchor bolt. For a particularly consistent and reliable result, a defined torque should be applied in this case to the nut, for example, with the aid of a torque wrench, in order on the one hand to ensure a sufficient expansion of the expansion sleeve and, on the other hand, to prevent potentially adverse excess stress on the expansion mechanism.
Another expansion anchor is known from DE 101 06 844 A1. In this expansion anchor, the extraction of the anchor bolt in order to expand the expansion sleeve is accomplished by a spring element. The known expansion anchor is inserted with the pre-stressed spring element into the bore hole. A holding mechanism is subsequently detached and the spring element is released.
A generic expansion anchor emanates from WO 97/32631 A1. This publication describes an expansion anchor for sport climbing having a spring element, which is tensioned in the bore hole when the anchor is inserted, and which then activates the expansion mechanism.
DE 33 31 097 C2, U.S. Pat. No. 1,583,849 A and DE 30 22 011 A1 describe expansion anchors having spring elements, which are able to maintain the pretensioning in the anchor, even if structural changes in the substrate should occur after the setting operation. Additional expansion anchors having spring elements are known from EP 0 461 790 B1 and DE 7 334 026 U.